Two and three-position selector switch



Jan. 9, 1968 F. W. KUSSY 3,363,070

TWO AND THREE-POSITION SELECTOR SWITCH Filed Dec. l, 1965 3 Sheets-Sheet l JPL- i Z INVENTOR.

y Ffa/VK W Aff/51s y Jan. 9, 1968 F. W. KUSSY TWO AND THREE-POSITION SELECTOR SWITCH Filed Dec. l, 1965 aff: 19070 HRA/ 5 Sheets-Shea#l 2 II- Ji.

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Jan. 9, 1968 F. w. KUSSY 3,363,070

TWO AND THREE-POSITION SELECTOR SWITCH' Filed Dec. l, 1965 5 Sheets-Sheet 5 .IIE- Z l 72 I 70 7l 4g 52 2'4/ /2/ /z S 72? United States Patent O 3,363,070 TWO AND THREE-POSITION SELECTGR SWITCH Frank W. Krissy, Birmingham, Mich., assigner to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Dec. 1, 1965, Ser. No. 510,841 8 Claims. (Cl. ZOU-51.17)

ABSTRACT F THE DISCLOSURE A selector switch convertible between two and threeposition capabilities including a housing and a movable carrier assembly rotatably mounted transversely with respect to the housing. The carrier assembly includes a handle and a bridge-carrying member, the front surface of which includes two distinct groups of notches which cooperate with a protrusion provided on the rear surface of the housing to cam the movable contacts of the carrier assembly into engagement with associated stationary contacts provided on the rear of the housing.

This invention relates to a selector switch and more particularly relates to a selector switch which may be easily converted from a three-position switch to a twoposition switch, or vice-versa.

As is well known in the art, motor starters, that is, electro-mechanical devices which are selectively operable between open circuit and closed circuit positions, have been found useful for establishing an electrical path between a source and an electric motor. Typical motor starters ininclude a coil which, when energized, actuates a cooperating armature to close the contacts of the starter and thereby establish a current path between a source and the motor being controlled.

To energize the coil of the motor starter, various control characteristics are desirable, depending upon the use of the motor starter. In many applications it is suicient that a simple two-position on and olf switch be provided in series with the motor starter coil, whereby manual movement of the switch to the on position (commonly known as the hand position) will energize the coil to operate the motor starter. In other applications it is desirable to manually operate the motor starter from a remote position or to automatically operate the starter in response to some predetermined condition. In such applications it is customary to provide a three-position switch in series with the motor starter coil, the three positions of which include: on (hand) for manual operation at the location of the switch; ofi which isolates the motor starter coil from its associated energizing source; and auto which places the motor starter coil in series with either a remote manual switch or in series with a device for energizing the motor starter coil in response to a predetermined condition.

The instant invention is directed to a selector switch which may be simply and easily converted between two and three-position capabilities and thereby eliminates the costs and manufacturing problems inherent in producing, storing and supplying both two-position and three-position switches.

As will be explained in greater detail, to convert a switch of the instant invention between its two modes of operation, eg., two and three-position characteristics, one merely loosens a screw, disconnects a wire, and changes the face plate of the switch to indicate the change in operating characteristics. It is apparent that such simple steps may be performed by relatively unskilled personnel, either in the factory, during manufacture, or in the field.

Although the instant invention has been described with Frice respect to the control of motor starters, it is to be understood that the instant invention is applicable to any environment which might require the use of a two-position and/ or three-position switch.

In its preferred embodiment the two and three-position selector switch of the instant invention includes a housing which may be molded or otherwise formed of electrically nonconducting material. A movable carrier assembly, which includes a handle and a bridge carrying member, is rotatably mounted transversely with respect to the plane of the housing such that a hand grasping portion of the handle extends forward of the housing while a smaller cylindrical portions of the handle extends through an aperture of the housing and is removably secured to the bridge carrying member. To prevent unintended relative displacement between the bridge carrying member and the handle, the engaging surfaces of these members are provided with an interlocking feature which can only be defeated by loosening the securing means which removably secures the bridge carrying member to the handle. The rear of the housing is provided with a plurality of pairs of electrical contacts which are arranged such that the individual contacts of each pair will be electrically joined through a conductive bridge which is carried at one end of the bridge carrying member when the switch is in the preselected hand and auto positions when the switch is functioning as a three-position switch, and when the switch is in the on position when the switch is functioning as a two-position switch.

To provide both two and three-position capabilities, the face portion of the bridge carrying member, .e., that portion of the bridge carrying member which is in rotatable engagement with the rear surface of the housing, is provided with two groups of inwardly directed peripheral notches at diametrically opposed circumference areas thereof which cooperate with a depending protrusion provided on the rear surface of the housing to seat the bridge carrying member in its proper positions. To change the switch from two-position to three-position operation, or vice-versa, one merely loosens the fastening means which secures the bridge carrying member to the handle, thereby defeating the interlocking feature noted above, and rotates the bridge carrying member whereby the oppositely disposed group of notches will now be in position to engage the protrusion depending from the rear surface of the housing. The fastening means is tightened once more whereby the bridge carrying member will be firmly tightened against the handle to prevent relative rotation therebetween.

As a further feature of the instant invention the front surface of the housing and the handle are provided with cooperating interference members which prevent the handle of the selector switch from being rotated beyond a predetermined arc which corresponds to the arc dened by the auto and hand position when the switch is operating as a three-position switch, and which arc corersponds to the arc defined by the on and off positions when the switch is operating as a two-position switch. Thus an operator cannot rotate the handle beyond the predetermined limits of the outermost switch positions.

Accordingly, it is an object of the instant invention to provide a selector switch which may be easily converted between two-position and three-position operation.

It is another object of the instant invention to provide a selector switch which comprises a housing having a yfront surface and a rear surface; a movable carrier -assembly mounted on the housing for rotation about an axis extending transversely to the front surface, such movable carrier assembly including a conductive bridge carried thereby and being selectively movable between a rst mode of operation wherein the carrier assembly may be selectively rotated between a rst, second and third circuit control position, and a second mode of operation wherein the carrier assembly may be selectively rotated between the first and third control positions; and a plurality of contactsmounted on a rear surface of the housing with pairs of such plurality of contacts being spaced on the rear surface to complete a path for electrical conduction between the contacts of each pair through the conductive bridge when the carrier assembly is in said first and third circuit control position.

Yet another object of the instant invention is to provide a selector switch which is capable of being changed in the the factory or in the field between two-position and three-position operation by relatively unskilled personnel. Y

Still another object of the instant invention is to provide such a selector switch whereby the convertability from two-position to three-position operation, or viceversa, is accomplished by a device which has a minimum number of parts and is thereby extremely dependable throughout extended periods of operation.

Other objects and a fuller understanding of the inst-ant invention may be had by referring to the following ydescription and drawings, in which:

FIGURE 1 is an exploded perspective view of a selector switch constructed in accordance with the teachings of theinstant invention; l

FIGURE 2 is a side view, partially in section, taken along the arrows 2 2 of FIGURE 1;

FIGURE 3 is a view taken along the arrows 3-3 of FIGURE l;

FIGURE 3A is a view taken along the arrows 3A-3A of FIGURE 3;

FIGURE 4 is a View taken along the arrows 4v4 of FIGURE 1;

FIGURE 4A is a view taken along the arrows 4A-4A of FIGURE 4;

FIGURE 5 is a view showing the bridge carrying member of the selector switch of the instant invention positioned to function as a three-position switch;

FIGURE 6 is a view similar to FIGURE 5 but showing the bridge carrying member adapted to operate as a two-position switch;

FIGURE 7 isa partial view of the circuit diagram and contact arrangement for FIGURE 1 and` showing the switch operating in its three-position mode 0f operation;

FIGURE 8 is a view similar to FIGURE 7 but showing the circuit diagram and contact arrangement for the switch of FIGURE 1 when it is in its two-position mode of operation;

FIGURE 9 is a view of the selector switch of FIGURE 1, with an indicating cover placed thereon, with such cover plate providin-g an indication of three-.position operation;

FIGURE 10 is a view similar to FIGURE 9, but showing the cover plate used when the switch is in its twoposition operation; and

FIGURE 11 is a side view partially in section of an alternative embodiment of the instant invention;

Referring to FIGURE l, there is shown a selector switch 10 which includes a housing 12 which may be molded or `oth'erwise formed of `electrically nonconductive material. The housing 12 includes a -front surface 14 and a rear surface 16 (see FIGURE 2) with an aperture 18 passing therethrough. Surrounding the aperture 18 and extending forward thereof is a hollow cylindrical shell 20 within which rotatably resides handle 22. Cylindrical shell 20 is supported by ribs 21 upon which cover plate brackets 23 may be removably secured by fastening means 25. Handle 22 together with a bridge carrying member 24 cooperate to define a movable carrier assembly which is mounted on the housing for rotation about an axis extending transverse to the front surface 14.

As seen in FIGURES 1 and 2, the rear surface 16 of housing 12 is provided with a plurality of pairs of electrical contacts 26, 28 and 38, 32, respectively, which are spaced on the rear surface so that contacts 26 and 28, or contacts 30 and 32 will be electrically connected through the conductive bridge 34 on bridge carrying member 24 when the selector switch is seated in certain preselected positions. Contacts 26, 28, 30 and 32 are each provided with a terminal post, in the form of screws 27, 'by which leads (not shown) may be electrically and mechanically and mechanically connected to the contacts.

As seen most clearly in FIGURES 1 and 3, the handle 22 includes a cylindrical central portion 36 havingV an enlarged head portion 38 upon which is provided an arrowshaped hand-grasping knob 40. At the opposite end of the cylindrical central portion 36 is provided a longitudinally extending projection 42 which is adapted to pass through the aperture 18 in the housing 12 4and be received by the projection receiving slot 44, provided on the Iface 46 of the bridge carrying member 24. The enlarged head portion 38 of handle 22 further includes a depending skirt 48 which seats kon a shelf 50 which surrounds the aperture 18 through housing 12, when the handle 22 is inserted within the cylindrical shell 20. The interior of the shell 20 is provided with an upstanding interference member 52 which engages either end 54 or 56 of depending skirt 48 when the handle 22 is rotated in either of its two directions. It will be apparent that interference of member 52 with depending skirt 48 limits the rotational movement of handle 22 to an arc, illustratively shown as 110 in FIG- URE 3, which is defined by the missing arcuate section of depending skirt 48.

Bridge carrying member 24 carries the Aconductive bridge 34, having contact pads 58 and 60 at opposite ends thereof, in a notched recess 62 provided at one end of a generally cylindrical center portion 64. The opposite end of the bridge carrying member 2-4 comprises the face portion 46 in which is provided the projection receiving slot 44 and a pair of oppositely disposed notch arrangements 66 and 68. Notch arrangement 66 includes three inwardly directed peripheral V-shaped notches 70, 72 and 74 (see FIGURES 4 and 5), spaced apart, preferably about 55. Notch arrangement `68 includes V-shaped notches 76 and 78 spaced apart by about 110. It is noted that notches 70 and 78, and 74 and 76 are spaced apart by 180 while notch 72 is located mid-way between notches 70 and 74 and is parallel to the conductive bridge 34. Notches 70, 72, 74, 76 and 78 cooperate with a depending tapered protrusion 80 provided on the rear surface of shelf 50 c(seeilFIGURE 2) in a manner to Ibe described in greater In assembling the selector switch of the instant invention, the handle 22 is inserted within the cylindrical shell 20 such that the interference member 52 resides within the arc provided between ends 54 and 56 of depending skirt 48. The lower surface of depending skirt 48 bottoms on shelf 50 so that ends 54 and 56 of the skirt and interference member 52 limit the rotation of handle 22 to 110. For a purpose to be further explained, a

biasing spring 81 is interposed between the shelf 50k of aperture 18 and the lower surface 82 (see FIGURES 3 and 3A) of enlarged head portion 38 of handle 22.

With the lower portion of depending skirt 48 seated on shelf 50, as explained above, the central cylindrical portion 36 (and elongated projection 42) of handle 22 extend through aperture 18 and is removably secured to bridge carrying member 24 by means of a screw 84 which passes throughl the conductive bridge 34 and aperture 86 in brldge carrying member 24 and into screw threaded engagement with a tapped aperture 88 in handle 22. A spring 89 interposed between the head of screw 84 and the conductive bridge 34- maintains the pads 58 and 60 of conductive bridge 34 in firm electrical engagement with the pairs of contacts 26, 28 and 30, 32, respectively, when circuit connections are made.

With the bridge carrying member 24 in the position shown in FIGURE 1, the screw 84 is tightened into handle 22 until the elongated projection 42 of handle 22 is interlocked in the projection receiving slot 44 in the face 46 of bridge carrying member 24. Such arrangement prevents relative rotation between the bridge carrying member 24 and handle 22.

Assuming that notch 72 in face portion 46 is aligned with the tapered protrusion 80 on the rear surface of the shelf 50 of housing 14, it will be seen that conductive bridge 34 will be parallel with supporting ribs 21 of housing 12, and therefore the pads 58, 60 will not engage either of the two contacts pairs 26, 28 or 30, 32 (see FIGURE 5).

Since biasing spring 81 urges handle 22 away from the front surface 14 of housing 12, and since bridge carrying member 24 is secured to handle 22 by screw 84, it will be apparent that the face 46 of bridge carrying member 24 will be urged into engagement with the rear surface of shelf 50 (see FIGURE 2) such that the tapered protrusion 80 will be firmly seated within notch 72. As will be described in greater detail with respect to FIG- URES 5 and 6, such positioning of the conductive bridge 34 corresponds to the off position when the selector switch is being used as a three-position switch.

If the handle 22 is now rotated clockwise in the direction of arrow 92 of FIGURE 1, the interlock provided between projection 42 and projection receiving slot 44, on the handle 22 and bridge carrying member 24, respectively, will assure that the face 46 of bridge carrying member 24 will be rotated relative to the fixed protrusion 80 whereby at the end of the rotational movement, the notch 70 will be rmly seated on protrusion 80 and terminal pads 58 and 60 will he in firm electrical engagement with contacts 26, 28 to complete an electrical path therebetween.

Similarly, if the handle 22 is rotated counterclockwise in a direction of arrow 94, face 46 of bridge carrying member 24 will be rotated in the direction of arrow 94 whereby notch 74 will seat itself upon protrusion 80 and terminal pads 58 and 60 will be in firm electrical engagement with contacts 30 and 32.

It will be noted that resilient spring 81 continually urges handle 22 away from the front surface 14 of the housing 12 thereby firmly seating the notches 70, 72 and 74 of the bridge carrying member 24 on the tapered protrusion 80. During rotation of the handle, the interaction of the protrusion 80 and the surface of the face member 46 between any two adjacent notches will cam the bridge carrying member in the direction of arrow 96 thereby drawing the handle 22 in the same direction against the bias of spring 81. When one of the notches 70, 72 or 74 seats on the protrusion 80 the spring 81 will expand driving the handle 22 and bridge carrying member 24 in a direction opposite arrow 96. As can be seen in FIGURE 5, notches 70v and 74 are displaced from one another by an angle of 110. Such angle corresponds to the arc of permissive motion of handle 22 as defined by the missing arc section of depending skirt 48 (see FIGURE 3). Thus the limits of rotatonal movement of handle 22 correspond exactly to the displacement of notches 70 and 74 and thereby prevent an operator from rotating the handle 22 beyond the seating position defined by notches 70 and 74.

An application of the three-position mode of operation for the selector switch thus far described may be seen in FIGURE 7 wherein the coil 98 of a motor starter 100 is to be energized by a source 102 in response to various circuit paths established by the three-position mode of operation. With the arrow-head 40 of handle 22 pointing in the `direction shown in FIGURE l, i.e., parallel to the ribs 21, the notch 72 of bridge carrying member 24 is seated on protrusion 80 and the conductive bridge is parallel to the ribs 21. This corresponds to the off position shown in FIGURE 7 in which no current path is established between the source 102 and coil 98. A visual indication of such condition may be provided on the front of the selector switch by means of an index cover plate 104 which is removably secured to the cover plate brackets 23 (see FIGURE 9). When the handle 22 is rotated to the hand position, notch 70 will then be seated protrusion and conductive bridge 34 will electrically interconnect terminals 26 and 28 to energize the coil 98 to actuate the motor starter. Similarly, if the handle 22 is rotated to the auto position (see FIGURE 9) notch 74 will seat on protrusion 80 and the conductive bridge 34 will electrically interconnect contacts 30 and 32 whereby the coil 98 may be energized by closing remotely located switch 106, or in response to some other predetermined condition. For the purpose of convenient phraseology the handle and auto positions may be termed active -while the off position may be termed passive When it is desired that the selector switch function as a two-position switch, the following simple steps are taken. The screw 84 is loosened so that the bridge carrying member 24 may be separated from handle 22 to defeat the interlock of projection 42 and projection receiving slot 44. The bridge carrying member 24 is now rotated manually by 180 and the screw 84 tightened once more into handle 22. Thus notches 7 6 and 78 are now in position to cooperate with the protrusion 80 on rear surface of the shelf 50. FIGURE 6 shows the new position of notches 76 and 78 and as can be seen by referring to FIGURE 5 such positions are 180 away from the positions they occupied when the selector switch was in its three-position mode of operation. As indicated in FIG- URE 6, notches 76 and 78 are spaced from one another by with there being provided no notch (which couid correspond to notch 72) spaced therebetween. Thus in this mode of operation the bridge carrying member 24 may seat itself on protrusion 80 in only one of two positions. With handle 22 residing in its most clockwise position (with respect to FIGURE 1) as determined by end 54 of depending skirt 48 interfering with member 52, notch 78 will be seated on protrusion 80 and conductive bridge 34 will electricallyconnect contacts 26 and 28 to establish an electrical path between source 102 and coil 98 of starter 100 (see FIGURE 8). If handle 22 is now rotated counterclockwise 110 (in a direction of arrow 94 in FIGURE 1), end 56 of skirt 48 will engage interference member 52 and notch 76 will seat itself on protrusion 80 whereby conductive bridge 34 will electrically connect contacts 30 and 32. However, when the selector switch is used as a two-position switch, the electrical lead at contact 32 is disconnected thereby allowing the second position to function as an off position to isolate source 102 from coil 98. In the two-position mode of operation a cover 108 is indexed with an off and hand notation (see FIGURE 10) to provide a visual indication of the condition of the selector switch. In a corresponding manner as the three-position mode of operation, the hand position may be termed active, while the o position may be termed passive In FIGURE 1l is shown an alternative embodiment of the instant invention. As most of the elements in FIG- URE 11 are identical to those previously described, like elements have been identified by identical reference characters.

The switch of FIGURE 11 differs from the switch of FIGURES 1-10 in that a small, square-shaped, keying element is keyed Within square-shaped aperture 121 of bridge carrying member 24 and is adapted to fit within an appropriately shaped aperture 122 in handle 22. The enlarged stern portion 124 of screw 84 bears against one end of keying element 120 and thereby assures that its other end will reside within aperture 122 of handle 22 when the screw 84 is tightened into tapped aperture 88 of the handle 22.

Bridge carrying member 24 is freely fitting on keying element 120 so that there may be relative longitudinal motion therebetween. However, as long as the keying element is within the bridge carrying member there can be no relative rotational movement therebetween. Thus with 7, screw 84 tightened so that keying element 120 enters aperture 122 of handle 22, handle 22 may not be rotated relative to bridge carrying member 24.

Conductive bridge 34 is maintained on the enlarged stemportion 124 of screw 84 by spring 89 on one side and on spring 126 on the other. As explained previously, spring 81 continually urges handle 22 away from the front surface of the housing 12 thereby firmly seating the notches 70, 72, 74, 76 or 78 on the tapered protrusion 80. It is apparent therefore that in the switch of FIGURES 1-10, if one accidentally depressed the handle 22 against the'bias of spring 81, it would be possible for the circuit to be broken through the conductive bridge 34. The embodiment of FIGURE ll eliminates this possibility by allowing the bridge carrying member 24 to move longitudinally relative to the key element 120 and the conductive bridge 34 so that even if the bridge carrying member is moved rearwardly by accidental depression of handle 22, the conductive bridge will remain in contact with the contact pair it connects.

Conversion from the two to three-position mode of operation, and v-ice versa, is accomplished in the same manner as explained for the switch of FIGURES l-lO. The screw 84 is loosened, such that keying element 120 may be withdrawn from the square aperture 122 in handle 22. The bridge carrying member 24 is rotated 180 and the screw 84 retightened so that keying element 120 is reinserted into aperture 122.

There has thus been described a simple selector switch comprising a minimum number of parts and which is easily convertible by unskilled personnel between two and threeposition modes of operation.

Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now be apparent to those skilled in the art. Therefore, this -invention is to be limited, not by the specific disclosure herein, but only by the appending claims.

What is claimed is:

1. A selector switch comprising:

a housing having a front surface and a rear surface;

a movable carrier assembly mounted on said housing for rotation about an axis extending transverse to said front surface; said movable carrier assembly including a conductive bridge carried thereby; said carrier assembly being selectively movable between a first mode of operation wherein said carrier assembly may be selectively rotated between a first, second and third circuit control position, and a second mode of operation wherein said carrier assembly may be selectively rotated between said first and said third -circuit control positions; and

a plurality of contacts mounted on the rear surface of said housing, pairs of said plurality of contacts being spaced on said rear surface to complete a path for electrical conduction between the contacts of each pair through said conductive bridge when said carrier assembly is in said first and third circuit control positions;

said housing and said carrier assembly having cooperating first and second interference means, respectively, for limiting the rotational movement of said carrier assembly to an arc which extends between said first and third control positions when said carrier assembly is in either of its two modes of operation;

said housing and said carrier assembly having cooperating cam means for accurately seating said carrier assembly in said first, second, and third control positions when said carrier assembly is in said first mode of operation, and for accurately seating said carrier assembly in said first and said third control positions when said carrier assembly is in said second mode of operation.

2. The selector switch of claim 1, wherein said carrier assembly includes a bridge carrying member, handle means removably secured thereto, and interlock means said interlock means; separation of said bridge carryingV member from said handle means allowing said bridge carrying member to be rotated relative to said handle means to change said carrier assembly between said first and said second mode of operation, said first and second interference means cooperating to prevent rotation of said handle means beyond the limits of said arc.

3. The selector switch of claim 1, wherein: said housing has an aperture passing therethrough and an interference member rigidly positioned adjacent said aperture on said front surface; and said carrier assembly comprises: handle means including a cylindrical center portion having an enlarged head portion at one end thereof, an elongated projection at the opposite end thereof, and an arcuatey skirt portion Vdepending from said head portion toward said opposite end; and a bridge carrying member including a face portion having a projection receiving a slot therein; said carrier assembly being mounted on said housing such that the skirt portion of said handle means bottoms on said front surface and such that said elongated projection extends through said aperture into removable engagement with the projection receiving slot in the face portion of said bridge carrying member, said depending skirt and said interference member cooperating to prevent rotation of said handle means beyond said first and third circuit control positions. 4. The selector switch of claim 1, wherein: said housing has an aperture passing therethrough and an interference member rigidly positioned adjacent said aperture on said front surface; and said carrier assembly comprises:

handle means including a cylindrical center portion having an enlarged head portion at one end thereof, a rectangularly-shaped aperture at the opposite end thereof, and an arcuate skirt portion depending from said head portion toward said opposite end; and

a bridge carrying member including a face portion at one end thereof and a conductive bridge receiving slot at its opposite end thereof, said bridge carrying member having a rectangularly-shaped passageway extending centrally therethrough for the reception of a slidable rectangularly-shaped keying element, a portion of which extends partially out of said one end of said bridge carrying member; and a conductive bridge mounted in said bridge receiving slot for longitudinal motion relative to said bridge carrying member; said carrier assembly being mounted on said housing such that the Yskirt portion of said handle means bottoms on said front surface and such that said portion of said keying element extends through said aperture into removable engagement with the rectangularly-shaped aperture in said handle means, said depending skirt and said interferencermember cooperating to prevent rotation of Vsaid handle means beyond said first and third circuit control positions. 5.V The selector switch of claim 3, wherein the face portion of said bridge carrying member is provided with a first and second plurality of inwardly directed notches at opposing areas thereon, and the rear surface of said housing is provided with a depending protrusion which seats in selected notches of said first plurality of notches-when said carrier assembly is in said first mode of operation, and which seats in selected notches in said second plurality of lnotches when said carrier assembly is in said second mode of operation.

6. The selector switch of claim 5, wherein said bridge carrying member is provided with securing means for adjustably tightening said bridge carrying member into engagement with said handle means to prevent relative rotation therebetween, said carrier assembly being changed between its two modes of operation by loosening said securing means and rotating said bridge carrying member 186 with respect to said handle means.

7. The selector switch of claim 6, and further including biasing means located between the front surface of said housing and the enlarged head portion of said handle means for urging the face portion of said bridge carrying member into engagement with the rear surface of said 10 housing.

8. The selector switch of claim 6, wherein said rst and third circuit control positions are active control positions position is a passive control position when said carrier assembly is in said second mode of operation.

References Cited UNITED STATES PATENTS 1,085,398 l/l9l4 Barr. 2,946,871 7/ 1960 Smidt et al. 3,167,620 1/1965 Keyser et al. 20G-155 ROBERT K. SCHAEFER, Primary Examiner.

and said second circuit control position is a passive con- 15 H. BURKS, Assistant Examiner. 

